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// mini-httpd: this is a single threaded, event driven very basic http
// server designed for event streams.
//
// Copyright (C) 2021 Russell King.
// Licensed under GPL version 2. See COPYING.
//
// This is designed *not* to be a publically accessible HTTP server,
// but is designed to be used behind e.g. an Apache reverse proxy that
// sends X-Forwarded-* headers. The presence of these headers prevents
// the served data being updated maliciously - updates must be done
// directly to this server.
#include <gio/gio.h>
#include <stdlib.h>
#include <string.h>
#include "event-httpd.h"
#include "resource.h"
static GHashTable *resource_hash;
void close_client(struct client *c)
{
if (c->request)
g_free(c->request);
g_object_unref(c->data);
g_object_unref(c->conn);
g_free(c);
}
void respond_header(struct client *c, int error_code, const char *reason,
const char *headers)
{
g_output_stream_printf(c->out, NULL, NULL, NULL,
"HTTP/1.1 %d %s\r\n%s\r\n",
error_code, reason, headers);
}
void respond_chunk(struct client *c, const GString *s)
{
if (c->can_chunk)
g_output_stream_printf(c->out, NULL, NULL, NULL,
"%x\r\n%s\r\n", s->len, s->str);
else
g_output_stream_write(c->out, s->str, s->len, NULL, NULL);
}
static void respond_error(struct client *c, int error_code, const char *reason)
{
GString *headers, *body = NULL;
headers = g_string_new("Cache-Control: no-cache\r\n"
"Connection: close\r\n");
if (error_code != 204) {
g_string_append(headers,
"Content-type: text/html; charset=UTF-8\r\n");
if (c->can_chunk)
g_string_append(headers,
"Transfer-Encoding: chunked\r\n");
body = g_string_sized_new(1024);
g_string_printf(body,
"<html><head><title>%d %s</title></head>"
"<body>%s</body></html>",
error_code, reason, reason);
}
respond_header(c, error_code, reason, headers->str);
if (body)
respond_chunk(c, body);
g_string_free(body, TRUE);
g_string_free(headers, TRUE);
close_client(c);
}
static void finish(GObject *source, GAsyncResult *res, gpointer user_data)
{
struct client *c = user_data;
GError *error = NULL;
gsize len;
g_data_input_stream_read_line_finish(c->data, res, &len, &error);
if (c->resource->close) {
c->resource->close(c, c->resource);
c->resource = NULL;
}
close_client(c);
}
static void update(GObject *source, GAsyncResult *res, gpointer user_data)
{
struct client *c = user_data;
GError *error = NULL;
char *line;
gsize len;
line = g_data_input_stream_read_line_finish(c->data, res, &len, &error);
if (error || !line) {
if (error)
g_free(error);
close_client(c);
return;
}
c->resource->update(c, c->resource, line);
g_free(line);
g_data_input_stream_read_line_async(c->data, 0, NULL, update, c);
}
enum method {
GET,
UPDATE,
};
static void receive(GObject *source, GAsyncResult *res, gpointer user_data)
{
struct client *c = user_data;
struct resource *resource;
enum method method;
GError *error = NULL;
gsize len;
char *line, *uri, *query, *unescaped, *version;
line = g_data_input_stream_read_line_finish(c->data, res, &len, &error);
if (error || !line) {
if (error)
g_free(error);
close_client(c);
return;
}
// In the interest of robustness, servers SHOULD ignore any empty
// line(s) received where a Request-Line is expected.
if (!c->request) {
if (line[0])
c->request = line;
else
g_free(line);
g_data_input_stream_read_line_async(c->data, 0, NULL,
receive, c);
return;
}
// Continue reading the request headers (we discard them)
if (line[0]) {
// Detect any X-Forwarded-* header
// FIXME: should this be case-insensitive?
if (g_str_has_prefix(line, "X-Forwarded-"))
c->forwarded = TRUE;
g_free(line);
g_data_input_stream_read_line_async(c->data, 0, NULL,
receive, c);
return;
}
g_free(line);
// End of request. Parse it.
// Find the URI
uri = strchr(c->request, ' ');
if (!uri) {
respond_error(c, 400, "Invalid request");
return;
}
*uri++ = '\0';
// Find the version
version = strchr(uri, ' ');
if (!version) {
respond_error(c, 400, "Invalid request");
return;
}
*version++ = '\0';
// Check that the version is HTTP/1.x. We probably ought to
// parse the major version better, as leading zeros should be
// accepted.
if (!g_str_has_prefix(version, "HTTP/1.")) {
respond_error(c, 505, "HTTP Version Not Supported");
return;
}
// Split the query string
query = strchr(uri, '?');
if (query)
*query++ = '\0';
c->uri = uri;
c->query = query;
c->version = version;
// HTTP/1.1 and later can use chunked mode. Note that http 1.1
// allows leading zeros.
c->can_chunk = atoi(version + 7) != '0';
// Check the method
if (!strcmp(c->request, "GET")) {
method = GET;
} else if (!strcmp(c->request, "UPDATE") && !c->forwarded) {
// Update is only permitted if not forwarded through a
// proxy. NOTE: this is the only way we control access.
method = UPDATE;
} else {
respond_error(c, 501, "Not Implemented");
return;
}
// Unescape the URI
unescaped = g_uri_unescape_string(uri, NULL);
// Lookup the resource handler
resource = g_hash_table_lookup(resource_hash, unescaped);
if (!resource) {
respond_error(c, 404, "Not Found");
return;
}
c->resource = resource;
// We have a valid resource, start the response
switch (method) {
case GET:
if (!resource->get) {
respond_error(c, 204, "No Content");
close_client(c);
return;
}
if (resource->get(c, resource)) {
g_data_input_stream_read_line_async(c->data, 0, NULL,
finish, c);
} else {
close_client(c);
}
break;
case UPDATE:
if (!resource->update) {
respond_error(c, 204, "No Content");
close_client(c);
return;
}
g_data_input_stream_read_line_async(c->data, 0, NULL,
update, c);
break;
}
}
static gboolean incoming(GSocketService *service, GSocketConnection *connection,
GObject *source_object, gpointer user_data)
{
struct client *c;
c = g_new0(struct client, 1);
c->conn = g_object_ref(connection);
c->out = g_io_stream_get_output_stream(G_IO_STREAM(connection));
c->in = g_io_stream_get_input_stream(G_IO_STREAM(connection));
c->data = g_data_input_stream_new(c->in);
g_tcp_connection_set_graceful_disconnect(G_TCP_CONNECTION(connection),
TRUE);
/* Be tolerant of input */
g_data_input_stream_set_newline_type(c->data,
G_DATA_STREAM_NEWLINE_TYPE_ANY);
g_data_input_stream_read_line_async(c->data, 0, NULL, receive, c);
return TRUE;
}
int mini_httpd_init(int port, const char *progname)
{
GSocketService *service;
GError *error = NULL;
service = g_socket_service_new();
if (!g_socket_listener_add_inet_port(G_SOCKET_LISTENER(service), port,
NULL, &error)) {
g_printerr("%s: %s\n", progname, error->message);
return 0;
}
g_signal_connect(service, "incoming", G_CALLBACK(incoming), NULL);
return 1;
}
int main(int argc, char *argv[])
{
resource_hash = g_hash_table_new(g_str_hash, g_str_equal);
resource_init(resource_hash);
if (!mini_httpd_init(1180, argv[0]))
return 1;
g_main_loop_run(g_main_loop_new(NULL, FALSE));
g_assert_not_reached();
}
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